Basic Siemens question, S7-300 dummy module.

[Elcan]

Hi all,
I'm starting learning Siemens from scratch. I have to use a S7-300 Siemens PLC in a project. There's a change more pieces of equipment will be added to the plant in the future (and I already need 8 modules), so I'm trying to follow an advice I found in a Siemens manual:
"If you opt for installation on a single rack, insert a dummy module to the right of the CPU (order no.: 6ES7 370-0AA01-0AA0). This gives you the option of inserting a second rack for your application in the future, simply by replacing the dummy module with an interface module and without having to reinstall and rewire the first rack."
I had thought this dummy module will be placed in slot 3, since in the TIA selection tool this slot 3 is reserved for an interface module. However, the TIA selection tool does not allow me to insert a dummy module in slot 3.
Therefore, my question is, if I add a dummy module to the right of the CPU, can I still have 8 I/O modules or just 7 (placing the dummy module in slot 4?)

Thank you!

 

[JRW]

Slot 3 is reserved for an IM (interface module)
with 1 dummy module- you can only have 7 I/o modules (in the main ur rack)

 

[TurpoUrpo]

IM's are for expansion racks. So i dont see the problem here. Me myself would still go for profinet expansion, but i dont know the spec or desing so.

 

[Mike_RH]

For expansion racks I would go to DP or PN as well. When you price out the hardware it works out about the same.

 

[KalleOlsen]

Hi all,
I'm starting learning Siemens from scratch. I have to use a S7-300 Siemens PLC in a project. There's a change more pieces of equipment will be added to the plant in the future (and I already need 8 modules), so I'm trying to follow an advice I found in a Siemens manual:
"If you opt for installation on a single rack, insert a dummy module to the right of the CPU (order no.: 6ES7 370-0AA01-0AA0). This gives you the option of inserting a second rack for your application in the future, simply by replacing the dummy module with an interface module and without having to reinstall and rewire the first rack."
I had thought this dummy module will be placed in slot 3, since in the TIA selection tool this slot 3 is reserved for an interface module. However, the TIA selection tool does not allow me to insert a dummy module in slot 3.
Therefore, my question is, if I add a dummy module to the right of the CPU, can I still have 8 I/O modules or just 7 (placing the dummy module in slot 4?)

Thank you!

Leave space on the leftmost rack side, and move the CPU when you need to insert the IM. No dummy needed.

Kalle

 

[Elcan]

Thank you everybody for your comments!
I have many questions:

1. Why the TIA selection tool reserves slot #3 even if I use only one rack? This makes the first I/O card (or SM card) always be module #4. What will happen in the programming software? Will my first I/O card be #4, even if I don't have an interface module?
2. Interface modules. The TIA selection tool offers 3 optiosn to me: IM 360, IM 361 and IM 365. Any recommendations?

3. Leave space on the leftmost rack side, and move the CPU when you need to insert the IM. No dummy needed.

   Is it as easy as it sounds?

Bear with me, please!

 

[Mike_RH]

Slot #3 can be considered a "logical" slot, even if you don't use an IM, slot 3 is used.
Slot 2 = CPU
Slot 3 = IM
Slot 4 = first SM module even if there is no IM.

 

[JRW]

Where are you located in NC?
Typically your distributor will give you a quick start
Wesco?